The ABC's new true crime podcast, Trace, re-examines the mysterious murder of Maria James. Find out why one former top cop can't stop digging, even in his retirement, and why her two sons have never given up hope.

The house was dark inside and there was no sound. John moved into the kitchen and called out down the hallway. There was no answer.

Enveloped with dread, he picked up a small green-handled knife from the kitchen drawer, and started inching through the house —first into the lounge room, then to the boys' room. Both were empty.

Next he entered Maria's bedroom and flicked on the light. There on the floor, eyes and mouth open, drenched in blood and covered in stab wounds, lay Maria.

"At this time, according to police, the killer was mere metres from John, hiding behind the door."

Distressed and confused, John ran out of the house without seeing the killer, found a nearby phone and called police. He paced up and down the laneway, before coming back around to the front of the bookshop.

This time, the door to the shop was open. There was someone inside; a woman browsing the shelves.

She told John that the door, which had been locked minutes before, had been open when she walked in.

Maria James was fully clothed when she was stabbed 68 times in the front and back of her body.

Her hands were bound — most likely after she was killed — and she was dragged across the floor of her bedroom in a frenzied attack police described as "bizarre".

Detectives believed whoever killed her would have been covered in blood from the attack.

They also suspected that the murderer would have been known to Maria James.

John was certain the other individual he could hear down the phone line was someone familiar to Maria.

Two coffee cups on her kitchen counter added further weight to the theory.

The killer has never been found

By modern standards, the investigation of Maria James' murder was strange.

In the days following her death, a team of homicide detectives set up shop in Maria's living room, out the back of the High Street Thornbury bookshop. It was considered easier to work directly out of there, rather than commute from the Fitzroy police station.

Every day, they would walk past the blood-stained carpet of the bedroom crime scene to their makeshift office.

Hers was his very first case as a homicide detective. Over the ensuing decades, Iddles achieved a staggering 99 per cent rate of cases solved.

But this one has remained unsolved, and it's one he can't let go.

For months, Iddles has assisted the Trace podcast team in reinvestigating Maria James' murder.

He is confident someone in the community holds critical information that could help solve the case.

"There is absolutely no doubt whoever killed Maria told somebody. And they're the people that we should appeal to," he said.

"They're the people who on their conscience should come forward so that both Mark and Adam can have the answers that they deserve."

Subscribe to Trace to follow the investigation

Trace is a new true crime podcast re-investigating the unsolved murder of Maria James.Join reporter Rachael Brown as she pursues previously discounted leads and uncovers new information that could hold the key to uncovering Maria's murderer.